Adding vents to an existing heating system... advice?

[Rezarf]

Not exactly garage topic here, but I feel the info could help others who have similar questions... searched and turned up nothing.

I moved into a new home this past summer that had a 75% complete basement. However, the previous owners did not drop vents (heat) into any of the rooms. I am a total newb when it comes to HVAC stuff, but I am hoping I can tap into a few heat duct lines and provide heat to the two bedrooms down there?

I am sure there is more to it than that, but I am hoping for some advice as to where to start? Here is my plan...

• I have access to 4 different heat ducts from unfinished space, can I "tap" into one of those for each room and add a vent? This would be at ceiling height. I am not sure if I would need to drop it down to floor level, as heat rises.
• I also need to add returns... at least I assume I would. Is it as easy as tapping into those with an equal size vent?
• I am trying to consider if I will mess up a "tuned" system. Our home heats very efficiently now, I'd hate to throw it too far off.

I am hoping to sheet rock this holiday weekend so feel free to speak up and not be shy

 

[HVAC Phil]

#1 You can't tap into any existing heat runs. You must run the new heat run back to the main trunkline.
#2 Sometimes the current trunkline isn't sized correctly to supply air to the new heat runs and current ones without changing the mainline. If it isn't sufficient, and you add 4 new runs, the new runs won't work properly and airflow to the others will suffer as well.
#3 Heat runs in the cieling work fine, i do it all the time...but you will need return air, in each room for it to heat properly.

I just repaired a system where someone added 4 heatruns to the trunkline. The trunkline was fed with 16x8 duct that currently had 8 heat runs off of it. It was marginal at best, useless after adding the new runs. I changed the ductwork on that side of the basement, now the house worked better and the basement worked great. Homeowner never had airflow output like that since house was new.

 

[Rezarf]

Thanks HVAC Phil, I appreciate it.